UTC - Urban Traffic control
Last updated | 28/08/2007
Urban Traffic Control (UTC) is a term used to describe the technique of co-ordinating traffic signals, normally through a centrally located computer. Areas, where signals are relatively close together and traffic flows are high, lend themselves to co-ordination as benefits are achieved by progressing platoons of traffic in an organised fashion. The system used to co-ordinate the traffic signals by the Council is called SCOOT.
The three parameters of cycle time, green split and offset are set to the most appropriate values to accommodate the prevailing traffic conditions and hence a number of plans will be available to be automatically loaded by computer at different times of the day.
The first UTC area in the United Kingdom was introduced by the Department of Transport in the late sixties and was extended throughout the country in the seventies. In London, over 500 signals are co-ordinated and controlled by a central computer and the benefits, which are well documented, amount to almost £80m per annum as a result of the reduction in delay to traffic.
The Council's Urban Traffic Control team
SCOOT - Split Cycle Offset Optimisation Technique
In the late seventies the Transport Research Laboratory (www.trl.co.uk) developed a new strategy known as SCOOT, which on a second by second basis operated a co-ordinated traffic control system without recourse to settings calculated on historical data.
The system utilised sub-surface inductive loops to detect traffic conditions and the resulting data was transmitted to the central computer where the optimisation process calculated the most appropriate settings of the cycle time, green split and offset.
Data is transferred via dedicated telephone lines from the street. Congestion and loop occupancy are monitored continuously and the program makes small amendments to cycle time offsets and splits. If the modification in one or more of these parameters improves the Performance Index (PI) then this change is made permanent and a further step is made in the same direction until no further improvement is made.
UTC Service Standards
The Council has set the following traffic signal service standards:
Type |
Timescales |
| Traffic Signal Faults |
Attendance within 4 hours |
| Red Lamp Faults |
Attendance and repair within 1 full day from notification |
| Routine Lamp Faults |
Attendance and repair within 2 full days from notification |
In some instances the traffic lights are affected by a fault on the electricity supply cable, which is the responsibility of the local electricity company to repair. Although the Council has a service level agreement which provides that these faults are repaired within the 5 working days, attendance and repair, particularly during the winter period, cannot always be guaranteed by the electricity company due to other priorities e.g. dealing with faults affecting household supplies.
